Electrical connector



June 1, 1954 F. L. PIERCE 2,680,235 ELECTRICAL CONNECTOR Filed Sept. 16,1949 2 Sheets-Sheet l ATTORNE June 1, 1954 P|ERE 2,680,235

ELECTRICAL CONNECTOR Filed Sept. 16, 1949- 2 Sheets-Sheet 2 4242;, wm wzATTORNEYS.

Patented June 1, 1954 UNITED STATES TNT OFFICE ELECTRICAL CONNECTORFrank L. Pierce, Camp Hill, Pa., assignor to Aircraft-Marine ProductsInc., Harrisburg, Pa.

Claims.

This invention relates to electrical connectors for use on insulatedwire, and to the methods of making and applying such connectors. Theinvention relates particularly to insulation-piercing solderless typeconnectors.

Prior to this invention, it has been proposed to secure connectors toinsulated wire by crimping the connector around the outside of theinsulation and. driving a sharpened conductive barb through theinsulating sheath to the central conductor to complete the electricalcircuit between the terminal and the conductor. For example, connectorshave been proposed having sharp barbs or prongs extending upwardly fromthe bottom of a trough-like wire-engaging ferrule portion. The insulatedconductor was intended to be pressed down upon these barbs so that thebarbs would pierce the insulation sheath to make contact with theconductive core of the wire, the ferrule then being pressed around theoutside of the insulation of the wire.

Such connectors can be attached to the insulated wire easier and morerapidly than the more usual type of connectors wherein the insulationmust be stripped from the wire and the connector then crimpcd orsoldered to the wire core. However, the solderless insulation-piercingconnectors proposed prior to the present invention have not replacedother connectors for most applications because, in practice, theelectrical connections produced by such connectors have not beensatisfactory. This is in part because low contact resistance of theconnector requires not only that the connector make contact with theconductive core of the wire, but that the two contacting members bemaintained continuously under sufiicient pressure that enough actualpoints of contact are established and maintained to carry the requiredcurrent. Thus, with some suggested constructions the normal fatigue ofthe metal of the connector with aging causes enough decrease in contactpressure to interfere with the performance of the connector. Anotherdifiiculty has been that the area of the connector making contact withthe conductive wire core has been small as compared with thecross-sectional area of the wire with the result that the connectors didnot have sufficient current-carrying capacity for many applications.

Still another disadvantage of earlier connectors is that, subsequent totheir being pressed onto an insulated conductor, the plastic orsemifiuid nature of the insulating sheath would allow the centrallylocated conducting core to move away from the contacting barbs therebydecreasing the efiectiveness of the electrical con- 2 nection. Thisdrifting of the center conductor under the influence of the appliedforces has been most troublesome with non-braided insulation sheathssuch as rubber and the like. Moreover, the mechanical strength,particularly the tensile strength, in insulation piercing connectors,has generally been poor, especially when the conductor is insulated withsuch soft, semi-fluid, or rubber-like insulation.

It is an object of the present invention to provide a solderlessinsulation-piercing connector that makes a good electrical connectionand that is simple and economical in use and which, in a large measure,overcomes the disadvantages of earlier solderless type connectors. Inone embodiment of the invention a wire-engaging ferrule portion isprovided with an inwardly extending sharpened barb positioned betweentwo oppositely-disposed ear portions which are adapted to be circled anddriven inwardly on or into the conductive core of the wire so as toclamp the conducting core of the insulated wire firmly in compressionbetween the ear portions and the barb thus holding the wire in excellentcontacting relationship with the connector irrespective of concurrent orsubsequent flow, or distortion in the shape of the insulating material.

In addition to providing for the transverse gripping of the conductingcore, as mentioned above, the invention also provides for anchoring theconductor against axial movement with respect to the connector byproviding an additional pair of oppositely disposed ears, displacedaxially a substantial distance from the first pair, which also grip theinsulating material and extrude it under pressure into the space betweenthe two sets or ears, thereby increasing the mechanical strength,particularly in tension, of the assembly and maintaining continuedclamping force on the conductive core, thus insuring mechanical andelectrical stability under normal conditions of use for a long period oftime.

Thus, in one aspect, this invention is directed to a simple connectorstructure and method of its application to insulated wire which providesa connection of excellent electrical stability and high tensilestrength. In another aspect, this invention is directed to an electricalconnector of the insulation-piercing type which is electrically andmechanically secure and which has substantially highencurrent carryingcapacity than is known in such connectors in the prior art. Anotheraspect relates to an electrical connector and method of applicationwhich will make and maintain secure electrical connection of highcurrent capacity with an electrical conductor even through a relativelylarge thickness of a pliable insulation sheath. These and other aspects,objects, and advantages of the invention will in part be pointed out in,and will in part become apparent from the following description whenconsidered in conjunction with the accompanying drawings, in which:

Figure 1 is a perspective view of a strip of electrical connectorsembodying the invention, for use in automatic connector-assemblingmachinery;

Figure 2 is an enlarged plan View of the connector shown in Figure 1;

Figure 3 is an elevational view of the connector shown in Figures 1 and2;

Figure 4 is a sectional view of the connector shown in Figure 1, takenalong line s-c of Figure 3, and an insulated conductor in a diestructure for assembling the connector and conductor;

Figure 5 is a perspective view of the connector of Figure 1 after beingassembled with an insulated conductor;

Figure 6 is a cross-sectional view taken along line 56 of Figure 5;

Figure 7 is a perspective view of a connector showing another embodimentof the invention.

Figure 8 is an isometric vi w of the connector shown in Figure 7 afterbeing assembled with an insulated conductor;

Figure 9 is a cross-sectional view taken along line 99 of Figure 8;

Figure 10 is a sectional view similar to Figure 9 showing anotherembodiment of the invention;

Figure 11 is an isometric view of a plug type connector representingstill another embodiment of the invention;

Figure 12 is an isometric view of the connector shown in Figure 11assembled with an insulated conductor; and,

Figure 13 is a cross-sectional view taken along line l3--l3 of Figure12.

Components serving similar functions in difierent embodiments of theinvention have been designated by adding one hundred to the indicatingnumerals of such similar components in each succeeding embodiment Figure1 shows a group of electrical connectors which have been fabricated in acontinuous strip to facilitate handling and their use in automaticmachinery, which cuts apart the individual connectors, generallyindicated at 2, and assembles them with the insulated conductors. Eachconnector 2 includes a wire-engaging ferruleforming portion, generallyindicated at 4, shown here as a trough-like channel, and a secondaryconnecting portion, generally indicated at d, shown representationallyas a forked or spadetongue connector, such as is used for making aconnection to a screw-type binding post or the like, which is formedintegrally with the ferruleforming portion 4 to which it is joined by aneck portion 1.

The ferrule-forming portion 4 (see also Figures 2 and 3) includes a baseportion 8 having two pairs of upwardly extending, oppositely-disposed,lateral ears l2 and I l which are spaced from each other axially, thatis, longitudinally along the axis of the connector. The base 8 isprovided with two upwardly extending, spaced, barbs or prongs i6 and i8which are positioned near the longitudinal center line of the connectorand, respectively, between each pair of opposed ears l2 and It. Byplacing at least a portion of each of the barbs i6 and 18 between anadjacent pair of the ears in the same transverse plane,

that is, in a plane extending at right angles to the longitudinal axisof the connector and through a pair of opposed cars, a clamping orgripping action on the conductor core is obtained, as will be describedlater. The connector advantageously is formed of corrosion proofedsteel, but other materials such as copper or brass can be used ifdesired.

Figures 5 and 6 show a connector 2 assembled with a conventionalinsulated conductor, generally indicated at 22, having a centrallylocated metallic conductive core 24, formed in this example of twistedwire strands, surrounded by a sheath 2% of insulating material. Theforward ears M have been curled sharply inwardly and driven end-wisedown through the insulating sheath 26 and between the strands of theconductive core 24, thus making intimate contact with these strands overa substantial area. Such piercing of the strands is not always used; ascraping contact which clamps the entire conductor between the earportions H3 is sometimes preferred, and will be illustratedsubsequently.

In order to assemble the connector 2 with the insulated conductor 22,the conductor 22 is placed in the trough of the ferrule-forming portion1 of the connector, which is positioned in a die structure, generallyindicated at 28 in Figure 4. The upper die 32 includes spaced parallelwall portions it, which extend, respectively, into sharply curvedportions 36, which at their juncture form a sharp ridge 38, which ifdesired can be somewhat blunted to reduce wear on the die. The lower die42 drives the connector 2 and the upper die 32 together curling the earsHl, as they follow along the inwardly curved die surfaces 35, anddriving them downwardly end-wise into the insulated conductor 22. Diessuch as this can be used in automatic machines which sever the connector2 from its strip during the cycle in which the connector is crimped ontothe conductor 22. This method of curling laterallyopposed ear portions,is disclosed more fully in the copending application of James C. Macy,Serial No. 717,842, filed December 23, 1946.

The ear portions l2, in this embodiment, are curled around the peripheryof the insulation sheath 2G, by a portion of the die structure 28 orother suitable means (not shown) and compressed and cold-workedthereagainst so that the ears l2, exerting pressure through theinsulation 26, clamp the conductor core 24 firmly down upon the barb H5thereunder. These ears i2 and the ears hi exert a compressive force onthe deformable insulation sheath 26 resulting in an outwardly extendingbulge 36 of insulation between the ears l2 and the ears M.

The above-described arrangement results in several advantageous featureswhich may not be entirely apparent from the structural description. Forexample, the barb i8 is disposed in a transverse plane (perpendicular tothe longitudinal axis of the connector) through the ears l4, so that theconductor core is driven down upon the barb l8 and held compressivelythereagainst by the faces of the tips 44 of the ears id. The contactpressure between the ears and barb l8 and the conductor core 24 is madeand maintained at a high value without depending upon transmission ofthese forces through the insulating material, and the conductor core isfirmly locked in position so that it cannot drift or work away from theareas of contact, thus assuring good conductivity even at low voltages.This arrangement is of particular importance when relatively thick orpliable insulating material is used.

In addition, the barbs It and i8 can be fabricated economically bycutting two oppositely directed V-shape notches in the base 8 offerruleforming portion 4 and bending the severed portions of the baseupwardly to form the barbs. The resulting openings in the base 8 must besumciently small that the ferrule is not weakened excessively, but thebarbs must be long enough to insure adequate contact with the core 24 ofthe insulated conductor 22. Moreover, the strength and orientation ofthe barbs must be such as to prevent the barbs from bending downwardlyinstead of piercing the insulation when the connector is assembled.Accordingly, after the initial formation of the barbs, by stamping orother means, the barbs are swaged, or otherwise shaped, to form apointed and sharpened projection, which process results in lengtheningof the barbs and at the same time making it easier for the barbs topenetrate the insulated conductor 22. The final length of the barbsadvantageously is at least equal to one-half the transverse width of thechannel of the ferruleforming portion 4, so that the barbs are at leastequal to the radius of any circular conductor placed in theferrule-forming portion i. In order to prevent the barbs from bendingtoward the openings which resulted from their formation, the barbs arebent slightly beyond the vertical position, so that the point of eachbarb is directly above the solid portion of the ferrule channel at thejunction of the base 8 and the barb.

In order to provide maximum contact area between the cars It and theconductor core 26, the ears i i are generally quadrilateral in shape andthe upper ends of these ears are rectilinear in the direction of thelongitudinal axis of the core 25, so that substantially greater contactarea is achieved than if the ears were formed in a generally triangularconfiguration, and larger surface areas are effective in clamping theconductor core 2% between the ears Hi and the barb I8.

In order that the ears M can readily penetrate the insulation, andextend between the strands of the core 24 where that is desired, theupper end of these ears are reduced in thickas by swaging. such as thoseshown at M for use in curling dies of the type shown in Figure suchknifeedge-like configuration has been found, helpful in preventingbuckling of the ears during crimping and in obtaining early conformationof the ear portion [5 with the die surface during the crimpingoperation, which assures that the ear portions M assume the propercurvature for making contact with the conductor core 2 3 in the desiredprecise manner, as well as in enhancing the ability of such ear portionsto pierce the insulation sheath 26 of the conductor 22.

Such swaging of the ear tips is advantageous also for the ears l2 as itenables the ears to be simply wrapped around and compressed down uponthe insulation sheath with the curled set of the ears extending to theirtips, thus giving the compacted ears a smoothly curved surface wherethey meet.

It is to be noted also that the forward edges d3 of the ear portions i2,which are compressed around the insulation sheath and co-operate withthe ear portions id to extrude, by virtue of their compression upon thesheath 2%, the previouslymentioned bulge 48 of insulation, are substan-In adapting ear portions 6*. tially rectilinear and at least partiallyabut the adjacent edges of bulge d6 of insulation. The firm grip thusobtained on the insulation by the ears l2 and it also increases andhelps to maintain the compression of the insulation in the area ofcontact and increases the support of the con ductor core. Furtheradvantages derive from the fact that the bulge as of insulationmaintains a continued. pressure between the insulation sheath 2B and theear portions !2 and it; this has been found to retard the entrance ofcorrosive fluids into the area of contact between conductor core 2%, theear tips 4%, and the barbs it and 58.

It is to be understood that the rearward ear portions 42 also can bedriven into contact with the conductor core 24, as are the cars it, toprovide even greater area of contact. Such an arrangement isadvantageous where maximum current-carrying capacity is desired.

In the above embodiment, the ear portions it are so constructed, and theupper die 32 is so designed, that the car tips M are curled away fromeach other in the connection, thus clamping the conductor core 2:;between the faces of tips it and the barb it. The ears are shown taperedin thickness from each side to form the km'feedges on their uppersurfaces, which aid in enabling the ear tips 4-5 to curl readily in thedie 23, as previously discussed. Note also the lateral separation, as at5d, of the ears Hi at their points of entrance into the insulationsheath 2E, leavin a portion of the insulation sheath 26 compressed inthe space 54 between the cars it, thus giving the contact area addedprotection against the entrance of corrosive fluids.

In some instances, such separation of the ears it, or even the curlingapart of their tips 84 can be advantageously replaced by maintaining theabutting face-to-face relationship of the ear tips at, which occursearly in their curling and crimping cycle, in the completed connection.Thus the ears it remain in actual contact with their tips cantedoutwardly so as to produce a lateral clamping effect analogous to thatshown in Figure 6, though of lesser degree, which tends to restrain theconductor core 25 from moving laterally.

In the above embodiment wherein three metal portions are drivenadjacently into the conductor 22, the final stages of compression of thewireconnector assembly is opposed by the reaction of the compressedwire, and, particularly with small wires or those having insulationsheaths which are relatively thin, tough, or lacking in pliability, thecompression of the insulation sheath should be relieved by holes in theconnector walls, either in the base or ear portions, into which theinsulation can extrude and allow proper setting of the ear portions.With suihciently thick and pliable insulation sheaths, extrusion intothe hole in the base portion 8 left by the upturned barbs is E8, plusthe longitudinal axial extrusion, is usually sufficient to permit suchproper setting.

Figures 7, 8 and 9 show another embodiment of the invention wherein aconnector, generally indicated at 182, includes a secondary connector inthe form of a tip E and a ferrule-forming portion, generally indicatedat Hi4, having two upwai'dlyextending, opposed, generallyquadrilaterally-shaped ears H4. These ears extend axially along theconnector blank for a suflicient distance to encompass twoupwardly-extending barbs H8, similar to the barb it of Figure 1.

Figure 9 shows a vertical section through the connector I02 afterassembly with an insulated conductor 122, having an inner conductivecore 5%, either solid or stranded, and an outer sheath 526 of insulatingmaterial. The: ears H 1 curve upwardly around the outside of theinsulation I26 and thence downwardly into the insulation. The ends ofthe ears H4 are advantageously sharpened or swaged to form a knife-likeedge and the tips Md of the ears are oppositely curved, as by a diestructure, such as is shown at 28 in Figure 4, with their surfaces inpressure contact with the outer surface of the conductor core 12 Thepointed barbs I18 extend upwardly from the bottom of the ferrule-formingportion I94 and make contact with the core i2 3.

Thus, the connector Hi2, at the position of each of the barbs H8, makesintimate contact with the conductor core I24 at three points spacedapproximately equidistant around its periphery, anchoring the core {2dfirmly in position and providing other advantages pointed out above.

With larger size conductors, or where the insulation is thin orrelatively rigid, it is not necessary to curl the ears Hi to obtain thisthree point clamping effect. Figure 10 shows an embodiment wherein theears He are curved upwardly, around the insulation 26, as above, but inwhich they extend downwardly through the insulation sheath I26 so thattheir rectilinear ends abut the upper surface of the conductor core I2i. Because of the relatively long axial length of the ears H4 andbecause contact between the ears H4 and the core I24 is maintainedsubstantially throughout the axial length of the ears, a relatively lowresistance connection is provided.

When conductors having thin or rigid insulation sheath are to be used incircuits that do not demand connections with high current ca pacity, theconnector can be made smaller and simplified, by using two sets oflaterally-opposed ears in a manner similar to that described inconnection with Figures 1 to 6, but in which the ears do not pierce theinsulation, but are wrapped around the insulation sheath and coldworkedto remove their elastic memory. If the ears are adjacent the upturnedbarb, the great compression thus acquired in the area of contactcompacts the insulation thereunder and reduces the likelihood that theconductor core will work 7 away from the barb.

Figures ll, 12 and 13 show such an embodiment of the invention wherein aconnector, generally indicated at 292, includes a ferrule-formingportion 294 and a secondary connector in the form i of a plug 256. Theferrule-forming portion 205 includes a channel-like base portion 288having two pairs of opposed, axially spaced, generallyquadrilaterally-shaped, ears 2I2 extending upwardly therefrom.

The connector is provided also with two barbs 2 IE each positionedbetween one of the two pairs of ears 2&2, the arrangement andconstruction being generally similar to the embodiment described inconnection with Figure 1.

Figure 12 shows the connector 282 after assembly with an insulatedconductor 222. In this embodiment, the ears 2G2 extend around theinsulation sheath 226, but do not pierce it. The compressive forceachieved by the spaced quadrilateral ears 2I2, which produces a bulge 215 of insulation between the ears, being relied upon to maintain thecontact between the conductor core 224 and the connector 202. Thisarrangement results in a simple and easily-assembled 8 connector whichis satisfactory for many purposes, but which can not be expected to haveso much current carrying capacity as the connector shown in Figure 1.

It is to be understood that the word connector is used herein in itsgeneric sense, including end terminals, terminals for connectinginsulated wires to binding posts, jacks, or the like, as well asconnectors for joining two or more lengths of wires.

From the foregoing it will be observed that the connectors embodying myinvention are well adapted for the attainment of the ends and objectsherein set forth and to be manufactured economically, since the separatefeatures are Well suited to common production methods and are subject toa variety of modifications as may be desirable in adapting the inventionto different applications. It is to be understood that many otherembodiments of my invention may be made and, accordingly, all matterhereinbefore set forth or shown in the drawings is to be interpreted asillustrative and not in a limiting sense.

I claim:

1. An electrical connection comprising an electrical conductor having acentral core of electrically conductive material and a surroundingcylindrical sheath of pliable insulating material, and a connector formaking electrical contact with said core including a ferrule portionsubstantially surrounding said sheath in compressive grippingrelationship and having three inwardly projecting portions, a first oneof which has a sharp point that penetrates the said core and the othertwo of which abut said core at two points generally opposite said firstportion thereby anchoring said central core firmly in position in saidconnection and making permanent electrical contact therewith.

2. An electrical connection comprising an electrical conductor having acentral wire core and a surrounding sheath of pliable insulatingmaterial, and a connector having a base portion, a barb extendingupwardly from said base and into said core, and two laterally-opposedear portions extending from opposite sides of the base adjacent saidbarb and around and in compressive engagement with said sheath, saidears being curled inwardly into said insulating sheath in opposediace-to-face relationship with the face of each of said ear portionsmaking pressure contact near its tip with said central core, said earsentering said insulation at spaced points on the surface of said sheathand a portion of the sheath being held in compressive engagement betweenthe adjacent surfaces of said ears.

3. An electrical connection including an electrical conductor having acentrally-positioned wire core and a surrounding sheath of pliableinsulation, and a connector having a ferrule portion including a baseportion extending along and in intimate pressure engagement with theouter surface of said insulation, a barb extending inwardly from saidbase and penetrating said central core, and a pair of laterally-opposedear portions extending from the said base around said sheath andinwardly into it outside said central core, said ears being in opposedface-to-face relationship at the point of entrance into said sheath andeach being in pressure engagement with the outer surface of said centralcore, said ears engaging said core at spaced points generally oppositesaid barb, said conductor being anchored in position between said barband the surfaces of said ears.

4. A connection comprising an electrical conductor having acentrally-positioned wire core and a surrounding sheath of pliableinsulation, and a conductor having a ferrule portion including a baseportion extending along and in intimate pressure engagement with theouter surface of said insulation, a sharpened barb extending inwardlyfrom said base and penetrating said core, and a pair oflaterally-opposed quadrilaterally-shaped ears having rectilinear endsextending substantially parallel with the longitudinal axis of saidconductor, said ears extending from opposite sides of said base aroundthe outer sur" face of said sheath and therein'to, the ears being inface-to-face relationship at the point of entrance into said sheath andsaidrectilinear end surfaces of said ears abutting said central coresubstantially opposite said barb.

5. An electrical connection including an electrical conductor having acentrally-positioned wire core and a surrounding sheath of pliableinsulation, and a connector having a ferrule portion including a baseportion extending along and in intimate pressure engagement with theouter surface of said insulation, a pair of laterally-opposedquadrilaterally-shaped ear portions having rectilinear ends extendingsubstantially parallel with the longitudinal axis of said central wirecore, said ears extending from opposite sides of said base around theouter surface of said sheath with their ends in substantially abuttingrelationship, the end portions of said ears exerting substantialcompressive force radially inwardly on said insulation, and a sharpenedbarb extending inwardly of said base between said ears, the end portionof said barb engaging said central core, substantial compressivepressure being maintained between said core and said barb by radialforce exerted by the oppositely-disposed end portions of said ears, saidbase portion having an opening therein adjacent said barb permittingextrusion thereinto of the insulation sheath to assure good mechanicaland electrical contact between said barb and the central core.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 379,688 Dennis Mar. 20, 1838 1,160,534 Schmidt Nov. 16, 19151,706,005 Thompson Mar. 19, 1929 1,816,674 Fortner July 28, 19312,197,578 Darnell Apr. 16, 1940 2,226,849 Douglas Dec. 31, 19402,302,767 Hackbarth Nov. 24, 1942 2,379,567 Buchanan July 3, 19452,476,429 Paules July 19, 1949 2,494,137 Martines Jan. 10, 19502,511,806 Macy June 13, 1950 2,600,012 Macy June 10, 1952 FOREIGNPATENTS Number Country Date 617,955 France Mar. 1, 1927

